WO2006048401A1 - Optimised turbine stage for a turbine engine and layout method - Google Patents

Abstract

A turbine (100) of a turbine engine is disclosed, in particular, a steam turbine for a steam turbine engine. The turbine comprises at least one radial or diagonal turbine stage (120) with radial or diagonal feed stream and axial exhaust flow and at least one axial turbine stage (121 - 125) with a axial feed steam and axial exhaust flow. The at least one radial or diagonal turbine stage (120) forms the first stage of the turbine (100) and the at least one axial turbine stage (121 - 125) is arranged downstream of the radial or diagonal turbine stage (121) as a further stage of the turbine. The at least one radial or diagonal turbine stage (120) has a higher temperature-resistance than the at least one axial turbine stage (121 - 125). The turbine (100) permits a significant increase in the process temperature of the steam turbine engine, whereby measures to increase the temperature-resistance need only be carried out on the components of the radial or diagonal turbine stage (120).

Description

OPTIMIZED TURBINE LEVEL OF A TURBINE SYSTEM AND DESIGN METHOD

Technical area

The invention relates to a turbine of a turbine plant, in particular a 5 steam turbine of a steam turbine plant. Furthermore, the invention relates to a method for designing a turbine and a method for operating a turbine system equipped with such a turbine.

State of the art

Due to the constant efforts to improve the efficiency of modern turbine systems, in particular modern steam turbine plants, it seems desirable to increase the process temperature of the turbine installations. An increase in the process temperature has an effect, on the one hand, in particular on the high-pressure turbine and, on the other hand, on the medium-pressure turbine of the turbine system which, as a result, is subjected to higher temperatures. As a result, even in steam turbines nowadays temperatures are already reached at which a use of conventional materials, in particular for the blading of the turbine, the flow channel walls and for the turbine shaft without temperature reduction measures, is no longer possible.

Such a temperature reduction measure can be, for example, to cool the blades of the turbine by means of a cooling fluid. Cooling of blades has long been known in gas turbines. However, for this purpose, on the one hand, a cooling fluid must be provided in a suitable manner, whether by external provision or by removal from one of the compressor stages of the turbine system. This leads to a deterioration of the overall efficiency of the turbine system. Also, in the case of film cooling or effusion cooling of the blades, aerodynamic losses are caused by the inflow of the cooling fluid into the main flow 0 of the turbine. Alternatively, the blades and, in some cases, the shafts of the turbine could be made of refractory materials, however, which makes the turbine very expensive to manufacture.

In addition to increasing the process temperature, an increase in the process pressure is usually sought. By increasing the process parameters, particularly within the first turbine stages of a high-pressure turbine, only relatively small volume flows of the flow-through fluid flowing through the turbine, mostly air or flue gas in gas turbines or steam in steam turbines, occur.

Small volume flows in turn cause small blade heights of the turbine blades with a small blade side ratio. As a result, it is often very difficult to design such turbine blading with a good aerodynamic efficiency.

Presentation of the invention

The invention aims to remedy this situation. The invention is thus based on the object of specifying a turbine of the type mentioned in the introduction and a method for designing a turbine with which the disadvantages of the prior art can be reduced or avoided.

The invention is intended in particular to contribute to increasing the efficiency of a turbine of a turbine system, in particular of a steam turbine of a steam turbine plant. According to a further aspect, the invention provides a kos¬ tengünstig manufacturable and efficiency-optimized turbine can be provided which can be acted upon by a high inlet temperature.

This object is achieved according to the invention by the turbine according to claim 1 as well as by the turbine system according to the further independent device claim, solved by the method for designing a turbine according to the first independent method claim and by the method for operating a turbine system designed according to the invention according to the further independent method claim. Further advantageous embodiments of the invention can be found in the subclaims.

The inventively embodied turbine comprises at least one radial or diagonal turbine stage with a radial or diagonal inflow and an axial outflow. By axial outflow is also to be understood an outflow, in which the flow at the exit from the impeller of the relevant turbine stage still has a diagonal flow direction, but at which the flow is then deflected by the flow duct in the axial direction before the flow passes into a subsequent turbine stage. Furthermore, the turbine designed according to the invention comprises at least one axial turbine stage with an axial inflow and an axial outflow.

Each turbine stage comprises at least one impeller. Usually, a turbine stage comprises a stator and an impeller downstream of the stator in the direction of flow.

In the context of the invention, the inflow and outflow directions can also deviate by a tolerance angle from the radial or diagonal and the axial direction, but the primary flow direction is retained as such.

The at least one radial or diagonal turbine stage is arranged as a first stage of the turbine and the at least one axial turbine stage is disposed downstream of the at least one radial or diagonal turbine stage as a further stage of the turbine. The at least one radial or diagonal turbine stage is designed so that it has a higher temperature resistance than the at least one axial turbine stage. The turbine according to the invention is preferably designed as a high-pressure turbine, which is arranged in a turbine system directly downstream of a combustion chamber or a steam generator of the turbine system. However, the turbine designed according to the invention can also be designed as a medium-pressure turbine or else as a low-pressure turbine, wherein then upstream of the medium-pressure turbine or the low-pressure turbine usually a reheater is arranged. Strom¬ from the inventively constructed turbine, one or more weite¬ re, trained in a conventional manner turbines can be arranged.

Since the radial or diagonal turbine stage embodied as the first stage of the turbine has a higher temperature resistance than the at least one axial turbine stage, the maximum process temperature which is present at the turbine unit during nominal operation can be higher than would be the case should the axial turbine stage form the entry turbine stage. The radial or diagonal turbine stage of the turbine designed according to the invention is capable of achieving a high enthalpy conversion, with the result that the temperature of the throughflow fluid at the outlet from the radial or dia¬ gonal turbine stage is significantly lower than at the entry into the radial or dia¬ gonal turbine stage. By means of only one radial or diagonal turbine stage, it is thus possible to lower the temperature of the flow-through fluid so far that no measures for increasing the temperature resistance of the components of the turbine, in particular of the blades, need be taken downstream of the radial or diagonal turbine stage to ensure that a maximum permissible material temperature of the components of the subsequent turbine stages is not exceeded. Such a measure could be, for example, the use of high-temperature material for the affected components or cooling of the components of the respective turbine stage by means of a cooling fluid. By arranging the radial or diagonal turbine stage as the first stage of the turbine, one or more measures need only be taken for the radial or diagonal turbine stage in order to increase the temperature resistance here. On the other hand, according to the conventional design, if the turbine only comprised axial turbine stages, then a plurality of axial turbine stages would be required in order to bring about the same enthalpy conversion and thus the same temperature reduction, as is the case with only one radial or diagonal turbine stage. Accordingly, suitable measures would have to be taken for these plurality of axial turbine stages in order to increase the temperature resistance of these axial turbine stages, so as to prevent a maximum permissible material temperature from being exceeded. A turbine which comprises only axial turbine stages is therefore considerably more expensive to produce when using high-temperature-resistant materials. If the affected components are cooled by means of a cooling fluid, cooling channels must be provided in the components on the one hand. On the other hand, the efficiency of the turbine is thereby deteriorated.

Especially in steam turbines, an embodiment of the first turbine stage proves to be advantageous as a radial or diagonal turbine stage also for the following reason. The steady increase of the process pressure leads to small volume flows of the flow-through fluid. For small volume flows, however, the efficiency of a radial or diagonal turbine stage suitable for this small volume flow is comparable to the axial turbine stages suitable for this small volume flow. In an overall efficiency balance, the turbine embodied according to the invention is thus often equally good or even better than a turbine which only includes axial turbine stages.

At particularly high inlet temperatures of the flow-through fluid, it may also be expedient to connect two or possibly even more radial or diagonal turbine stages in series at the inlet to the turbine. However, several radial or diagonal turbine stages again lead to an increase in the production costs. This also makes the flow path structurally complex, so that a solution with only one radial or diagonal turbine stage is to be preferred. In principle, at very high inlet temperatures, radial turbine stages are to be preferred over diagonal turbine stages, since radial turbine stages allow even higher energy conversion compared to diagonal turbine stages.

Particularly advantageously, the turbine designed according to the invention comprises exactly one radial or diagonal turbine stage and at least one axial turbine stage.

Although in the context of the description of the invention, for simplicity, only the turbine stage as a whole is discussed, the high temperatures of the flow-through fluid primarily affect those components of the turbine stage which are directly exposed to the hot flow-through fluid. In particular, these are the blades of a turbine stage as well as often the sidewalls of the flow channel, i. the hub and often the housing wall. Accordingly, measures to increase the temperature resistance are primarily also applicable to these components of a turbine stage. However, it should be noted that due to heat conduction also components that are not exposed to the hot Durchströmfluid can reach very high temperatures and then also measures for increasing the temperature resistance must be taken for these components.

In principle, the invention can be applied to turbines and turbine plants in general. However, the invention is particularly expediently applied to a steam turbine of a steam turbine plant. Dampfturbinenanla¬ conditions usually have large dimensions, which would result in conventional design of the steam turbine, a significant need for high heat resistant and thus expensive material, since several axial turbine stages would have to be made of this material. On the other hand, in the past, steam turbines were generally designed and operated in such a way that only comparatively low maximum process temperatures and simultaneously a large volume flow of flow-through fluid occurred. Due to the large volume flow, in turn, the use of a radial or diagonal turbine stage or a radial or diagonal turbine was not useful. Only through the combined increase In the case of steam turbines, the process temperature and the process pressure and the resulting reduction of the volumetric flow make the use of a radial or diagonal turbine stage meaningful and lead to an improvement in overall efficiency and / or lower production costs and to more compact steam turbine plants.

Suitably, the radial or diagonal turbine stage is made of a first material and the at least one axial turbine stage is made of a second material. The first material has a higher temperature resistance than the second material. Thus, the radial or diagonal turbine stage spielsweise be made of a high temperature nickel-base alloy, while the at least one axial turbine stage, for example, from a übli¬ Chen and cheaper cast steel or a nickel-chromium steel mit gerin¬ gerer heat resistance be made can. As has already been stated above, it should be noted that, however, not all components of a turbine stage must always be made from the high-temperature resistant material. So it is often sufficient to produce only those components of a high temperature resistant material, which are directly exposed to the hot Durchströmfluid, such as the blades and the shaft of the turbine stage.

In an alternative or supplementary embodiment of the invention, the radial or diagonal turbine stage is expediently designed with a coating of a highly heat-resistant material, for example a nickel-based alloy. In this case, however, it must be ensured that the base material, which is arranged under the coating and has a lower hot strength, is not overheated as a result of heat conduction. Optionally, it may be necessary here to additionally cool this material by means of cooling.

Alternatively or additionally, the radial or diagonal turbine stage is expediently made of a ceramic material or carried out with a coating of a ceramic material. Ceramic materials offer the advantage that the components not only have a higher heat resistance. but that the ceramic components or coated components also have a heat-insulating effect and thus, for example, a reduced heat input into the shaft takes place via the blade roots.

The at least one axial turbine stage may then be made of a conventional turbine material without coating.

In an alternative or supplementary embodiment of the invention, the radial or diagonal turbine stage is cooled. The at least one axial turbine stage here is preferably uncooled.

In an advantageous development of the invention, a step load of the radial or diagonal turbine stage turbine turbine is selected so that in a nominal operation of the turbine, the flow fluid at the entrance to the radial or diagonal turbine stage has a temperature which is higher than a maximum ¬ Permitted softening temperature of the material of the axial turbine stage, and at the outlet of the radial or diagonal turbine stage has a temperature which is equal to or less than a maximum allowable softening temperature of the material of the axial turbine stage. Conversely, this means that the maximum process temperature of the turbine system can be increased up to a maximum value at which the above condition is just fulfilled. Measures to increase the temperature resistance are thus limited to the radial or diagonal turbine stage.

The inventive arrangement of one or more radial or diago¬ nal turbine stages at the turbine inlet thus provides a possibility in a cost effective manner, the maximum process temperature of the turbine system er¬ significantly increase. In an economic analysis, the increase in the efficiency of the turbine system which can be achieved with this is only offset by the comparatively cost-effective measures for increasing the temperature stability of the radial or diagonal turbine stages. The turbine is expediently designed so that a mean outlet diameter of the radial or diagonal turbine stage is equal to a mean inlet diameter of the axial turbine stage following the radial or diagonal turbine stage. As a result, the flow channel between the radial turbine stage or diagonal and the axial turbine stage can be straight.

In an expedient embodiment of the invention, the radial or diagonal turbine stage and the at least one axial turbine stage are arranged on a common shaft. However, such a common arrangement of the turbine stages on a shaft is only possible if the turbine stages can be operated continuously at the same speed.

In an alternative embodiment of the invention, the radial or diagonal turbine stage is arranged on a first shaft and the at least one axial turbine stage on a second shaft, wherein the shafts via a transmission, preferably a planetary gear, are interconnected. Although such an arrangement of two waves is more complex compared to the arrangement of only one shaft; however, so different speeds of the turbine stages can be realized.

Furthermore, the radial or diagonal turbine stage and the at least one axial turbine stage are preferably arranged in a common housing.

In another aspect, the invention provides a method of designing a turbine. The method according to the invention comprises the method steps of arranging at least one axial turbine stage downstream of a radial or diagonal turbine stage and of carrying out the radial or diagonal turbine stage with a higher temperature resistance than the at least one axial turbine stage. The method according to the invention is suitable in particular for the design of the above-described turbine according to the invention. According to an advantageous development of the method a Stufenbelas¬ tion of the radial or diagonal turbine stage of the turbine is selected so that in a nominal operation of the turbine, the Durchströmfluid at the entrance to the radial or diagonal turbine stage has a temperature which is higher than a maximum allowable softening temperature Material of the axial turbine stage, and at the outlet of the radial or diagonal turbine stage has a temperature which is equal to or less than a maximum allowable softening temperature of the material of the axial turbine stage of the turbine.

In a further aspect, the invention provides a method for operating a turbine system, wherein the turbine system comprises a steam generator and a turbine arranged downstream of the steam generator and heat is supplied to a flow-through fluid in a combustion chamber or in a steam generator. The flow-through fluid is thereby heated to a temperature which is above a maximum permissible softening temperature of the material of the axial turbine stage of the turbine. Subsequently, the flow-through fluid in the radial or diagonal turbine stage of the turbine is expanded to such an extent that the temperature of the flow-through fluid at the outlet from the radial or diagonal turbine stage is equal to or less than the softening temperature of the material of the axial turbine stage of the turbine.

Brief description of the drawings

The invention will be explained in more detail below with reference to several exemplary embodiments, which are illustrated in the figures. Show it:

FIG. 1 shows a high-pressure turbine known from the prior art

Steam turbine plant;

FIG. 2 shows a first turbine designed according to the invention; FIG. 3 shows a second turbine designed according to the invention. In the figures, only the essential elements for the understanding of the invention elements and components are shown.

The illustrated embodiments are to be understood as purely instructive and are intended to serve a better understanding, but are not to be understood as limiting the subject matter of the invention.

Ways to carry out the invention

Figure 1 shows a known from the prior art, designed as a high-pressure turbine turbine 10 a steam turbine plant. The Durchströmfluid is here water vapor. The steam coming from a steam generator (not shown in FIG. 1) is fed radially to the turbine 10 via a live steam pipe 31. In the radial inflow portion of the main steam pipe 31, there is here a first stator 20LE for rectification and / or for pre-swirl generation of the steam flow. The vapor flow is then deflected in a deflecting section (in the region of the flow arrow 36) out of the radial flow direction (direction of the flow arrow 35) into an axial flow direction (direction of the flow arrow 37). Only after the deflection in the axial flow direction, the steam flow flows through the impeller 20LA of the first turbine stage and subsequently thereto the further axial turbine stages 21 - 28 of the turbine 10 arranged downstream of the first turbine stage. All turbine stages 21 - 28 with the exception of the first turbine stage 20 (= 20LE + 20LA) are designed as purely axial turbine stages. The first turbine stage 20 is designed here as a combined radial-axial turbine stage, wherein the stator 20LE in the radial inflow portion of the main steam pipe 31 and the

Impeller 20LA is arranged in the axially flow-through portion of the turbine designed as a high-pressure turbine 10 turbine. The energy conversion takes place aus¬ finally in the purely axially flowed through section. The amount of energy conversion is limited to the same extent as well as in the case of axial turbine stages because of the maximum flow deflection that can be achieved in axially flown wheels. If the steam supplied to the steam turbine now has a high or very high inlet temperature which is above the permissible softening temperature of the material usually used for blading the impellers and guide vanes, for example steel castings, then at least the flow channel forming the flow channel must and / or arranged in the flow channel Bau¬ parts of those turbine stages of the turbine, in the region of the steam has a temperature above the softening temperature, either made of a highly heat-resistant material or cooled in a suitable manner. In the example shown in FIG. 1, the first three turbine stages 20, 21 and 22 are affected. Here, both the blades of the first three turbine stages and the channel side walls of the flow channel are made of a highly heat-resistant material. At 40, the hot zone boundary is marked strom¬ must be taken on the measures to increase the temperature resistance. In many cases, due to heat conduction in this area, the shaft is made of a high temperature resistant material. In the nominal operation of the turbine 10, the steam has a temperature only downstream of the third turbine stage 22, which temperature is below the softening temperature of the material usually used for turbine components. By using highly heat-resistant material for the first three turbine stages 20, 21 and 22, the production costs for such a steam turbine become considerably more expensive.

This is where the invention starts. FIGS. 2 and 3 show turbines 100 designed as steam turbines according to the invention. In both exemplary embodiments, the turbines illustrated here each comprise exactly one radial turbine stage 120 with radial inflow (direction of flow arrow 135) and axial outflow (direction of flow arrow 137) ) and a plurality of axial turbine stages 121-125 each having an axial inflow and an axial outflow. The radial turbine stage 120, which is designed as a first stage of the turbine, adjoins directly to the radially extending part of a live steam nozzle 131. The axial turbine stages 121-125 are arranged in both exemplary embodiments immediately downstream of the radial turbine stage 120. In order to enable a charge of very hot steam, the radial turbine stages 120 shown in FIGS. 2 and 3 are each designed with a higher temperature resistance than the axial turbine stages 121-125. This is achieved, for example, by the radial turbine stage 120 each ¬ Weil is made of a high temperature nickel-base alloy or a kerami¬'s material, whereas the axial turbine stages 121 -125 are each made for example of a conventional cast steel or a nickel-chromium steel. As an alternative to the use of a high-temperature material or in addition thereto, the blades of the radial turbine stage 120 could also be designed either with a heat-insulating coating or with cooling.

The radial turbine stages 120 shown in FIGS. 2 and 3 thus geometrically essentially replace the radial-axial turbine stage 20 from FIG. 1. However, when the radial turbine stages 120 according to FIGS. 2 and 3 flow through, the temperature of the steam flow becomes lowered so far that the subsequent axial turbine stages 121-125 may be made of conventional turbine material. Since radial and also diagonal turbine stages 120 can be loaded significantly higher and can achieve a considerably higher enthalpy conversion than axial turbine stages, only one radial turbine stage is required in the embodiments of the invention shown here in order to sufficiently lower the temperature below the softening point temperature of the material of the axial turbine stages 121-125. In contrast, in the embodiment known from the prior art according to FIG. 1, three axial turbine stages 20, 21 and 22 were required for a sufficient temperature reduction. In the same conditions of Durchströmfluids at the entrance to the turbine in the inventive design of the turbine, as shown in Figures 2 and 3, therefore, only the components of the respective radial turbine stage 120 have a high temperature resistance. This therefore relates to significantly fewer components than is the case with conventionally designed turbines. Since, in addition to the process temperature, the process pressure is increased in order to achieve high efficiencies, only comparatively small volume flows of the throughflow fluid at the inlet into the turbines result. For small volume flows, however, radial or diagonal turbine stages have a similar efficiency as axial turbine stages. Therefore, the turbines shown in FIGS. 2 and 3 are also comparable in their overall efficiencies to the turbine of FIG. 1, but with significantly lower production costs and more compact dimensions.

In the following, the method for designing a turbine according to the invention will be explained with reference to the turbines 100 illustrated in FIGS. 2 and 3. Both examples assume typical geometric and other constraints for high pressure turbines used in steam turbine plants, i. E. A shaft diameter of about 880 mm and a rated turbine speed of 50 Hz. For designing the impeller of the radial turbine stage 120, the so-called "cordier diagram" known from the prior art (see, for example, Dubbel, Taschenbuch für den Maschinenbau ", 18th edition, R22) is used, in which for single-stage turbine engines a correlation between a diameter parameter ÖM in function of the specific speed OM is graphically reproduced, wherein:

, .1 / 4,. .1 / 2. , .1 / 2,. .3 / 4 δM = IΨyMl / IΦMI and OM = IΦMI / IΨyMl

2 with (PM = Cm / u _m and ψ _y M = Δh / (u _m / 2)

As a result, an acceptable efficiency of the turbine stage is guaranteed with an isentropic efficiency of about 90%.

In both embodiments, it is assumed that the inlet pressure at nominal operation of the turbine at the inlet to the turbine 300 bar and the Dampf¬ mass flow rate is about 400 kg / s. These are typical values for modern steam turbines. If the turbine inlet temperature is now to be 620 ° C., which is a typical value for a modern, supercritical steam turbine, the following values result with the aid of the Cordier diagram if an exit temperature of 565 occurs at the exit from the radial turbine stage ° C and less should be given:

(PM = 0.30, ψ _y M = 6.50 => OM «2.9, OM« 0.14

At a temperature of 565 ⁰ C and less, no measures for increasing the temperature resistance must be taken for the components downstream of the radial turbine stage, since this temperature value is below the softening temperature of the material commonly used for the axial turbine stages.

The radial turbine stage 120 thus configured generates a pressure drop of the steam of 300 bar at the inlet to the radial turbine stage to 217 bar at the exit from the radial turbine stage, i. the pressure ratio is around 1.4. The temperature at the outlet from the radial turbine stage is about 560 ° C. The rotational speed of the radial turbine stage is 50 Hz, with a mean diameter of 1120 mm and a blade width of 23 mm at the inlet and 41 mm at the exit.

The stator of the first axial turbine stage 121 arranged downstream of the radial turbine stage 120 can then operate with a typical axial inflow and a blade height of approximately 60 mm with an assumed flow coefficient of approximately 0.24. For this purpose, the stator of the first axial turbine stage 121 has a mean inlet diameter which is equal to the mean outlet diameter of the impeller of the radial turbine stage 120. Thus, a straight flow channel in the region of the transition from the radial turbine stage 120 to the axial turbine stage 121 can be realized. As has been clarified in the above embodiment, it is possible to design a radial or diagonal turbine stage so that it is at a typical nominal operating state of a steam turbine, in which the steam turbine is charged with steam at high or very high inlet temperature, works with a good efficiency. During operation, the turbine stage designed in this way ensures that the axial turbine stages arranged downstream are only exposed to ordinary, much lower temperature loads, even if the inlet temperature at the entry into the radial or diagonal turbine stage is significantly above an admissible softening temperature of the material of the axial turbine levels.

In addition, in the exemplary embodiment according to FIG. 2, the radial turbine stage 120 can be operated at the same speed as the axial turbine stages 121-125. This makes it possible to drive the radial turbine stage 120 and the axial turbine stages 121-125 as shown in FIG. to arrange on a common shaft 130. Also, a continuous, common housing 132 can be used here.

In the exemplary embodiment illustrated in FIG. 3, an inlet temperature into the turbine 100 designed as a steam turbine of 700 ° C. is assumed. This is a typical value for ultra-supercritical turbines. Again, exiting the radial turbine stage 120 requires a temperature of 565 ° C or less. These requirements result in the following parameters with the aid of the Cordier diagram:

(PM = 00:30; ψ _y M = 4:00 => ÖM ^{"2.6 OM"} 0:19

The thus designed radial turbine stage 120 generates a pressure drop of the steam flow of 300 bar at the inlet to the radial turbine stage to 145 bar at the outlet from the radial turbine stage, ie the pressure ratio is about 2.1. The temperature at the exit from the radial turbine stage 120 is about 565 ° C. The rotational speed of the radial turbine stage 120 is 100 Hz, with a mean diameter of DM 1120 mm and a blade width of 13 mm at the inlet and 32 mm at the outlet. The stator of the first axial turbine stage 121 arranged downstream of the radial turbine stage 120 can then operate with a typical axial inflow and a blade height of approximately 100 mm with an assumed flow coefficient of approximately 0.22. The stator of the first axial turbine stage 121 has a mean inlet diameter, which is equal to the average Aus¬ exit diameter of the impeller of the radial turbine stage 120. Thus, in the region of the transition from the radial turbine stage 120 to the first axial turbine stage 121, a straight throughflow channel can be realized. However, the rotational speed of the axial turbine stages 121-125 here is only 50 Hz, while the rotational speed of the radial turbine stage 120 is 100 Hz.

This exemplary embodiment shows that even in the case of a very high inlet temperature at the inlet to the turbine, starting from a typical nominal operating state of a steam turbine, it is possible to provide a radial or diagonal turbine stage as the inlet stage of the steam turbine. The thus designed and operating with good efficiency radial turbine stage 120 then ensures that the downstream axial turbine stages 121-125 are exposed to only significantly low temperature loads, even if the inlet temperature at the entrance to the radial turbine stage 120 very clearly is above a permissible softening temperature of the material of the axial turbine stages 121-125. The hot zone boundary 140, which must be taken upstream of the measures for increasing the temperature resistance, runs here between the radial turbine stage 120 and the first axial turbine stage 121.

However, in this embodiment, the radial turbine stage 120 and the axial turbine stages 121-125 are to be operated at different speeds, so that it is not possible here to arrange the radial turbine stage 120 and the axial turbine stages 121-125 on a common shaft. The high rotational speed of the radial turbine stage 120 results from the requirement to achieve a high temperature reduction or a high enthalpy conversion in the radial turbine stage. A high temperature reduction or a high enthalpy Turnover is only possible if either the radial turbine stage is designed to be rapidly rotating or, alternatively, the radial turbine stage has a very large diameter, or alternatively the blading of the turbine stage is aerodynamically very heavily loaded. The last two alternatives are unsuitable here, since a very large diameter would require very small blade widths and a very high aerodynamic loading of the blades would result in poor stool efficiency.

Therefore, it is convenient here to let the radial turbine stage 120 rotate faster than the axial turbine stages 121-125. The radial turbine stage 120 is therefore arranged on a partial shaft 130-1 and the axial turbine stages 121-125 on another partial shaft 130-11. In this case, it is possible for the first turbine section, which includes the radial turbine stage 120, as well as the second turbine section, which includes the axial turbine stages 121-125, to be on separate shafts, but in a common housing 132 or Also accommodate in two separate housings.

The two partial waves 130-1, 130-11 shown in FIG. 3 are connected to one another via a gear, not shown in FIG. However, the shafts can also be connected to one another via a planetary gear, wherein, for example, the partial shaft 130-1, on which the radial turbine stage 120 is arranged, the partial shaft 130-11, on which the axial turbine stages 121-125 are arranged, in the Pla¬ wraps around.

The turbines 100 shown in FIGS. 2 and 3 can be arranged as high pressure turbines of steam turbine plants, a steam generator then being arranged upstream of the fresh air stub 131.

The steam turbines shown in FIGS. 2 and 3 can, however, also be arranged as intermediate pressure turbines of steam turbine plants, wherein a reheater is then usually arranged upstream of the fresh air outlet. The turbines and turbine systems described in connection with FIGS. 2 and 3 as well as the methods described represent exemplary embodiments of the invention which can readily be modified by a person skilled in the art without departing from the spirit of the invention.

LIST OF REFERENCE NUMBERS

10 turbine

20LE stator of the radial turbine stage

20LA radial turbine stage impeller

21 - 28 axial turbine stages

30 wave

31 live steam pipe

32 housing

35, 36, 37 flow direction of the flow-through fluid

40 hot zone limit

100 turbine

120 radial or diagonal turbine stage

121-125 axial turbine stages

130 common wave

130-1, 130-11 partial waves

131 live steam pipe

132 housing

135, 136, 137 flow direction of the flow-through fluid

140 hot zone boundary

Claims

claims 1. Turbine (100) of a turbine plant, in particular steam turbine of a steam turbine plant, with at least one radial or diagonal turbine stage (120) with radial or diagonal inflow and axial outflow and with at least one axial turbine stage (121-125) with axial inflow and axial outflow, wherein each turbine stage comprises at least one impeller, and the at least one radial or diagonal turbine stage (120) is arranged as the first stage of the turbine and the at least one axial turbine stage (121-125) is downstream of the radial or diagonal turbine stage (120). is arranged as a further stage of the turbine, characterized in that the at least one radial or diagonal turbine stage (120) has a higher Temperature resistance than the at least one axial turbine stage (121-125). 2. Turbine according to claim 1, wherein the turbine exactly one radial or diagonal turbine stage (120) and at least one axial turbine stage (121-125). 3. Turbine according to one of the preceding claims, wherein the radial or diagonal turbine stage (120) made of a first material and the at least one axial turbine stage (121 - 125) made of a second Werk¬ material, wherein the first material has a higher Temperatur¬ resistant than the second material. 4. Turbine according to one of the preceding claims, wherein the radial or diagonal turbine stage (120) is coated with a coating of a temperature-resistant material tem¬. 5. Turbine according to one of the preceding claims, wherein the radial or diagonal turbine stage (120) is made of a highly heat-resistant nickel-based alloy or coated with a coating of a hoch¬ heat-resistant nickel-based alloy. 6. Turbine according to one of the preceding claims, wherein the radial or diagonal turbine stage (120) is made of a ceramic material her¬ or coated with a coating of a ceramic material. 7. Turbine according to one of the preceding claims, wherein the wenigs¬ least one axial turbine stage (121 - 125) made of a conventional Turbi¬ nenwerkstoff without coating. 8. A turbine according to one of the preceding claims, wherein the radial or diagonal turbine stage (120) is cooled and the at least one axial turbine stage (121-125) is preferably uncooled. 9. Turbine according to one of the preceding claims, wherein a step load of the radial or diagonal turbine stage (120) of the turbine is selected such that in a nominal operation of the turbine (100) a flow-through fluid at the inlet into the radial or diagonal turbine stage ( 120) has a temperature which is higher than a maximum permissible softening temperature of the material of the axial turbine stage, and the throughflow fluid at the outlet from the radial or diagonal turbine stage (120) Temperature which is equal to or less than a maximum allowable Er¬ softening temperature of the material of the axial turbine stage. 10. Turbine according to one of the preceding claims, wherein a temperature drop of the Durchströmfluids between the entry into the radial or diagonal turbine stage and the exit from the radial or diagonal Turbine stage at least 50 ° C, preferably more than 6O ⁰ C and insbe¬ special more than 120 ° C. 11. Turbine according to one of the preceding claims, wherein a mean outlet diameter of the radial or diagonal turbine stage is equal to a mean inlet diameter of the radial or diagonal Tur¬ binenstufe subsequently arranged axial turbine stage. 12. Turbine according to one of the preceding claims, wherein the radial or diagonal turbine stage (120) and the at least one axial turbine nenstufe (121 - 125) on a common shaft (130) are arranged. 13. Turbine according to one of claims 1 to 11, wherein the radial or dia¬ gonal turbine stage (120) on a first shaft (130-1) and at least one axial turbine stage (121-125) on a second shaft (130 11) are arranged and the shafts via a transmission, preferably a Plane¬ tengetriebe, are interconnected. 14. Turbine according to one of the preceding claims, wherein the radial or diagonal turbine stage (120) and the at least one axial turbine nenstufe (121 - 125) in a common housing (132) are arranged. 15. Turbine plant, in particular steam turbine plant, with a Brennkam- mer or a steam generator and with a turbine according to one of the preceding claims, wherein the turbine is arranged immediately downstream of the combustion chamber or the steam generator. 16. A method for designing a turbine, in particular for the design of the turbine according to one of claims 1 to 14, comprising arranging at least one axial turbine stage downstream of a radial or diagona¬ len turbine stage, and to carry out the radial or diagonal turbine stage with a higher temperature resistance than the at least one axial turbine stage. 17. The method according to claim 16, wherein a step load of the radial or diagonal turbine stage of the turbine is selected so that in one Nominal operation of the turbine, a flow-through fluid at the inlet to the radial or diagonal turbine stage has a temperature that is higher than a maximum permissible softening temperature of the material of the axial turbine stage, and the flow-through fluid at the outlet from the radial or diagonal turbine stage has a temperature, which is equal to or less than a maximum permissible softening temperature of the material of the axial turbine stage of the turbine. 18. A method according to any one of claims 16 or 17, wherein a temperature drop of the Durchströmfluids between the entry into the radial or diagonal turbine stage and the exit from the radial or diagonal turbine stage is chosen so that the temperature drop at least 50 ° C, preferably more as 6O ⁰ C and in particular more than 120 ° C. 19. A method of operating a turbine plant according to claim 15, wherein heat is supplied to a flow-through fluid in the combustion chamber or in the steam generator and the flow-through fluid is thereby heated to a temperature which is above a maximum permissible softening temperature of the material of the axial turbine stage of the turbine and subsequently the flow-through fluid in the radial or diagonal turbine stage of the turbine is released to such an extent that the temperature of the flow-through fluid at the outlet from the radial or diagonal turbine stage is equal to or less than the softening temperature of the material axial turbine stage of the turbine is.